Abstract :
The microgrid is a miniature power supply load and an independent control system to provide local power and heat. This concept provides a new model to describe the microgrid operation; microgrid can be seen in the power unit in a controlled, it can respond in seconds to meet the needs of the external transmission and distribution networks; on the user, the microgrid to meet their specific needs: increase local reliability, reduce feeder loss, to maintain local voltage, through the use of waste heat to provide higher efficiency, the voltage drop to ensure uninterrupted power supply or the provision of the amendment. The pattern of uneven economic development created a local energy concentration zone to the load center of mass, long-distance transmission of the base frame this site, this framework is that there is a natural defect energy consumption, inefficient use of power assets, the land area occupied many other issues, establish a complete set of integrated water, electricity, gas, heating, cooling, fresh air and other energy smart micro-net is a necessary repair pathway defects in the structure, which not only improves energy efficiency, but also a reasonable solution of the optimization of local energy resources use, energy efficiency strategy is one way. It can achieve a variety of energy conversion, easing pressure on the backbone of the energy transmission network, build regional smart energy network industry cluster, the internal implementation of peak load shifting in the micro-network to improve the energy efficiency of asset utilization, active local economy, promote coalbed methane, oil gas development wind power, photovoltaic power, biomass and other new energy development, to achieve a variety of complementary forms of energy. Different types of traditional energy sources and new energy (solar, wind, tidal energy, etc.) stored by energy storage of excess energy distributed power, such as superconducting coils, energy storage capacitors and energy sto- age capacity of a huge super-capacitors and flywheels, etc. and so on. Through a study of these techniques are a series of results, combined with power system requirements of users of power quality and power system development, these technologies will be gradually formed a comprehensive network together to form a special form micro grid. On their own microgrid for grid to its normal operation mode is one way of working. On the following issues: the power house, as a power unit failure, maintenance or other reasons out of operation the load increased dramatically, resulting in less need for power supply in parallel with the introduction of outside power grid; or because in some extreme cases, to meet the load and storage needs, there are still surplus power can be sent out in parallel with the external grid energy; and landed in the bus voltage, external power failure or grid-connected line tripping, etc., causing a sudden interruption of external power connection, micro power grid need to smooth operation mode from grid to an independent run mode, as a result of efforts can not balance the load caused by the inverter frequency deviation, etc., the paper had described one by one.
